Catheters are tube-like medical instruments that may be inserted into a body cavity, organ, or blood vessel for diagnostic or therapeutic reasons. Catheters may be designed for insertion into the vasculature and are available for a wide variety of purposes, including diagnosis, interventional therapy, drug delivery, drainage, perfusion, and the like. They may also be useful for other procedures, such as gynecological procedures, cardiac procedures, general interventional radiology procedures, and the like. Catheters for each of these and other purposes can be introduced to numerous target sites within a patient's body by guiding the catheter through an incision made in the patient's skin and a blood vessel and then through the body to the target site.
Catheters generally have an elongated, flexible catheter body with a catheter side wall enclosing one or more catheter lumens. The lumens can extend from a catheter body proximal end, where the catheter body is coupled to a relatively more rigid catheter hub, to a distal end. The one or more lumens may have the same diameter throughout the length of the catheter or taper, such as when the lumens have a larger diameter at the proximal end than at the distal end. The catheter hub typically has one or more access hubs that provide for the insertion of wires or the attachment of syringes or other devices, for example. The catheter body may be relatively straight, inherently curved, or curved by insertion of a curved stiffening wire or guide wire through a catheter lumen. The catheter body may assume a straight or linear configuration, when free from external bending forces. The catheter body may be highly flexible, thus able to pass through the tortuous twists and turns of a patient's vascu lature. In some cases, the catheter body may have a shaped distal end portion including curves and bends which are selected to facilitate introduction and placement of the catheter in the vascular system. A particular geometry of curves and/or bends may be selected to accommodate the intended use of the catheter. The distal end of the catheter may also be equipped with an inflatable balloon to expand a medical device, such as a stent, and/or to dilate a vessel.
The body and side wall of the catheter may be fabricated and dimensioned to minimize the outer diameter of the catheter body and the thickness of the side wall. In this fashion, the diameter of the catheter lumen may be maximized while retaining sufficient side wall flexibility and strength characteristics to enable the catheter to be used for the intended medical purpose.
The catheter body may have a length in the range from about 40 cm to 200 cm, usually having a length in the range from about 60 cm to 175 cm. The diameter of the catheter body may be in the range of about 0.67 mm (2 F) to about 7 mm (21 F). The catheter body may define one or more inner lumens that may have inside diameters ranging from about 0.4 mm to about 6 mm.
The body and/or side wall of the catheter may be made from any suitable material, including, but not limited to, polyethers and polyester block amides. For example, the side wall may be made from a polyether block amide, which may include a copolymer of amide monomers copolymerized with polyether monomers. Because the amide monomers may have greater structural “rigid ity” in comparison to the polyether monomers, the rigidity of the resulting catheter body to deformation, such as bending or stretching, may be controlled. One example of a suitable polyether block amide from which the catheter body and/or side wall may be made is PEBAX®, which is available from Elf Atofina, Philadelphia, Pa. In one aspect, a blend of PEBAX® polyether block amides may be used.
The catheter body may be constructed with one or more additional elongated, flexible bodies or tubes residing within the outermost body. Thus, the outermost tube may contain one or more inner tubes defining additional inner lumens. In this fashion, a first lumen may be formed in the interior of an inner tube, while a second lumen may be formed between an outer wall of an inner tube and the inner wall of the outermost tube. When an inner tube is placed substantially in the center of the outermost tube, the lumens may be coaxially arranged as shown in FIG. 3C.
The catheter may also be constructed with one or more longitudinal partitions that contact the outermost wall at two or more locations and reside within the outermost body. In this fashion, a first lumen may be formed between a first side of a partition and the outermost wall, while a second lumen may be formed between a second side of the partition and the outermost wall. In this arrangement, the lumens have separate centers. A catheter body having an internal arrangement of this type is depicted in FIG. 1A.
The inner tube or tubes that form the lumens may be made from a single material, such as a lubricious polymer, or a combination of materials. Lubricious polymers include, but are not limited to, fluorocarbons, such as polytetrafluoroethylene (PTFE), polyamides, such as nylons, polyether block amides (PEBA), polyolefins, polyimides, and the like. The inner tube may also be a laminate structure comprising a non-lubricious outer layer and an inner lumen surrounding layer or coating of a more lubricious material. When one or more lumens are formed by one or more partitions, the partitions may be formed from the same material as the outermost wall; however, this is not required.
The end of the catheter that remains external to the body cavity (proximal end) terminates in a catheter hub. A conventional catheter hub 14, such as that depicted in the catheter 100 of FIG. 1, is a single piece that is directly bonded to the catheter body 12 with an adhesive at one or more adhesive bonds 18. The conventional catheter hub 14 may include one or more access hubs, such as a first lumen access hub 15 and a second lumen access hub 16. The lumen access hubs provide ingress and egress from the mouths 17 of the access hubs to one or more lumens, such as the first lumen 26 and the second lumen 28, respectively. The lumens may have a substantially smaller diameter than the access hubs. The access hubs 15 and 16 may be female luer type connectors or another type of connector. A skive 20 is a passageway through a catheter side wall 13 of the catheter 100 and may provide fluid communication between the second lumen access hub 16 and the second lumen 28.
Fluids, gases, wires, and the like may be passed from the mouths of the access hubs, through the lumens, and optionally into the body cavity. For example, a stiffening or directing wire may be threaded through the first lumen access hub 15 and into the first lumen 26. This wire may then be utilized to guide the catheter through the body cavity. A fluid, such as a viscous liquid, pharmaceutical preparation, or gas, may be directed through the second lumen access hub 16, the skive 20, and into the second lumen 28. If the catheter 100 is a balloon type catheter, this fluid may inflate a balloon at the distal end of the catheter that is in fluid communication with the second lumen 28.
While the conventional catheter 100 can be effective, disadvantages exist for the conventional catheter hub 14. These disadvantages are in the areas of construction and performance. Regarding construction, when the hub 14 is assembled, the portion of the first lumen access hub 15 that tapers in diameter 30 to meet the first lumen 26 must be aligned with the first lumen 26. Because the first lumen 26 may have a relatively small diameter, on the order of a few millimeters or less, alignment can be difficult. It may also be difficult to form the first lumen junction 13, where the access hub 15 and the lumen 26 are bonded by adhesive or other means. It is also necessary to adhesively bond the catheter body 12 with the catheter hub 14, ensuring that the skive 20 aligns with the second lumen access hub 16. Such meticulous construction can be difficult and time consuming. Due to the small surface areas to which the adhesive may be applied, separation of the catheter body from the hub is also possible.
The conventional catheter hub 14 may also have performance disadvantages resulting from the entrapment areas 32 that reside between the second lumen access hub 16 and the catheter side wall 13 and at the proximal end of the second lumen 28. When a fluid is introduced into the second lumen access hub 16, especially if it is a viscous fluid, the fluid not only passes through the skive 20, but also exerts considerable pressure on the adhesive bonds 18 that hold the catheter side wall 13 to the catheter hub 14 in the area of skive 20. This flow is depicted as the second lumen flow 24. If too great, this pressure can lead to failure of the adhesive bonds 18 and result in separation of the catheter body 12 from the catheter hub 14. Thus, if a balloon is inflated at the distal end of the catheter with fluid introduced through the second lumen access hub 16, a limitation may be placed on the pressure to which the balloon may be inflated and the rate at which the fluid may be introduced to the balloon. This can lead to lengthy inflation times. Additionally, because there is little mechanical support in the area of the skive 20, the fluid may crush the side wall to some extent, thus reducing fluid flow into the second lumen 28.
Similarly, because fluid must pass from the second lumen 28, through the skive 20, and through the entrapment areas 32 before exiting through the second lumen access hub 16, a limitation is placed on how quickly the balloon may deflate. The entrapment areas 32 can disrupt and/or create turbulence in the fluid flow out of the catheter, thus significantly impeding deflation of the balloon.